Cells of many tissues are polarized, collectively forming configurations tailored to the needs of a tissue. A common feature of most cancers of epithelial origin is the loss of normal tissue architecture. Despite advances in identifying signaling pathways involved in driving cancer progression, little is known about how polarity is disrupted during transformation. Dr. David Bryant studies the molecular control of epithelial polarity. His long- term goal as an independent biomedical researcher is to understand how epithelial polarity goes awry during tumor formation. With this award, Dr. Bryant will examine the ADP-ribosylation factor (ARF) GTPase family and their regulatory molecules (the ARF 'regulome') in control of polarity during prostate cancer, as 'regulome' members are highly overexpressed in human prostate cancers. This K99/R00 award will allow Dr. Bryant to achieve the following career goals: 1) additional training in prostate biology, and human cancer genetics, 2) develop genomic skills for analyses of human prostate cancer gene expression, 3) gain skills in immunohistochemical and histopathological techniques to analyze tissue samples of human biopsies and mouse models of prostate cancer from in vivo, and 4) develop the communication, mentoring, grant-writing, and laboratory management skills necessary to become and successful, independent biomedical researcher. The mentored phase of this research will be carried out at the University of California, San Francisco under the guidance of Dr. Keith Mostov. During the mentored phase, Dr. Bryant will use the combined approaches of genetics, semi-automated microscopy, and in vitro spheroid culture of normal and tumorigenic prostate epithelial cells to define changes in ARF regulome expression that control prostate acinar morphogenesis (Aim 1). Next, he will elucidate the interplay between the ARF regulome and oncogenic pathways leading to castration-resistant prostate cancer (Aim 2). To identify potential disease stage-specific ARF regulome alterations during prostate cancer progression in vivo (Aim 3), Dr. Bryant will begin using genomic and immunohistochemical analysis of tumors from human patients and mouse models of prostate cancer of varying disease stage. Drs. Pamela Paris, Davide Ruggero (UCSF), experts in prostate cancer genomics and cancer genetics, respectively, will serve as collaborators and advisors. During the independent phase, Dr. Bryant will continue to focus on Aims 2 and 3, the mechanisms of ARF regulome-controlled epithelial polarity, and in vivo analysis of ARF regulome alterations in tumors. This award will enable Dr Bryant to examine the molecular regulation of prostate epithelial polarity in a rapid, medium-throughput fashion, enabling development of selective interventions that inhibit the ARF regulome pathway, and potentially identifying novel targets for therapeutic interventions in prostate cancer.